The present invention generally relates to digital imaging systems and more particularly to the fabrication of X-ray detector assemblies.
Digital X-ray imaging systems are becoming increasingly widespread for producing digital data, which can be reconstructed into useful radiographic images. In some known digital X-ray imaging systems, radiation from a source is directed toward a subject, such as a patient in a medical diagnostic application. A portion of the radiation passes through the patient and impacts a detector wherein the detector converts the radiation to light photons, which are sensed. The detector is divided into a matrix of discrete picture elements or pixels, and encodes output signals based upon the quantity or intensity of the radiation impacting each pixel region. Because the radiation intensity is altered as the radiation passes through the patient, the images reconstructed based upon the output signals provide a projection of the patient's tissues similar to those available through conventional x-ray photographic film techniques.
An important factor in medical imaging applications is a detector spatial resolution. Photons, which are generated in a scintillator material over one detector pixel, need to be counted only by that underlying pixel to obtain a high image resolution. Photons that are scattered to adjacent pixels reduce the clarity of the image. Therefore scintillator material is vapor deposited in columnar or needle form. Individual needles are separated from one another and possess aspect ratios (length/diameter) of about 100 or greater. Photons traveling down the scintillator needles tend to be contained within the individual needle due to the higher refractive index of scintillator material over air, provided that the individual scintillator needles remain separated. A Cesium Iodide (CsI) scintillator material is known to be a hydroscopic salt. Exposure of CsI scintillator material to moisture can cause the CsI scintillator material to absorb moisture, which further causes the individual CsI scintillator needles to coalesce or fuse together.
Transportation, storage and operation of radiation imaging equipment may expose the equipment to adverse environmental conditions, such as moisture from atmospheric humidity and splash during operation and shipping. Such environmental conditions have the potential to damage the radiation imaging equipment. For example, such imagers include a scintillator, which converts radiation into visible light, that may experience coalescence under such conditions, resulting in image degradation, potentially rendering the radiation imager unusable. The term “coalescence” refers to crystals of the scintillator growing together due to moisture absorption. Once coalescence begins, it may further spread beyond the initial point or area of damage.